The present invention relates to a snow melting apparatus and heating wire for melting snow, and more particularly to a snow melting apparatus and heating wire and adapted to be laid in driveways, walkways, parking lot or the like in regions having lots of snow for preventing accumulation of snow and freezing at those specific places.
In regions having lots of snowfalls, snow accumulating on the surfaces of driveways and frozen road surfaces endangers traffic travelling thereon and due to the accumulation of snow and frozen road surfaces There are caused traffic jams along driveways, often resulting in a paralysis of physical distribution.
With a view to preventing the accumulation of snow on the road surfaces and freezing thereof, on top of mechanically removing accumulating snow, there have been proposed many devices for removing snow in various ways. Raised as one of them is a method for laying underneath road surfaces electric heating apparatus using nichrome wires as a medium.
Japanese Utility Model Registration No. 3006758 discloses as a conventional electric heating apparatus a known road heater in which a linear heating element is covered with a fabric structure. This heater requires a continuos material to be laid while fixing it at appropriate positions, and such laying work is found inefficient. In addition, with such a continuous material, the diameter thereof tends to inevitably become larger to prevent increase in electric resistance, and this reduces the flexing capability of the material, which is then liable to break. Moreover, if the continuous material breaks even at a single position therealong, it leads to a problem that the whole heating apparatus fails.
Furthermore, Japanese Patent Unexamined Publication No. Hei.10-106729 discloses as a surface heating element a mat-like heating element in which a meandering conductor is covered with a flexible epoxy resin. This surface heating element is laid between a basic layer of concrete and a top or surface layer of asphalt. However, since the surface heating element completely separates the basic layer and the surface layer, it provides a problem that the strength of the road surface becomes weakened. In addition, since no flexing capability is provided, the heating element is not appropriate to be laid along a curved driveway. In addition, Japanese Patent Unexamined Publication No. Hei. 9-78517 discloses a snow, melting unit in which a linear heating element is laid on a net. Since this snow melting unit comprises a mesh-like net, the problem inherent in the aforesaid heating element is solved that it lacks the joining force between the base layer and he surface layer. However, due to its flexing capability, this linear heating element still suffers from the conventional problem that the element is difficult to be laid along a curved driveway. Also, another conventional problem remains unsolved; that is, since the element comprises a linear heating element, if it breaks even at a single position, the whole element fails.
In a construction site, the heating wires and power supply cords are electrically connected. However, in the connection work, it is required that the covers of the wires and cords are removed, and insulation sealing is applied to the joining portions by winding an insulating tape therearound. Additionally, the diameter of the heating, wire is different from that of the power supply cord. Accordingly, the connection work is complicated and troublesome. Further, there is a chance that heat by asphalt and load acting thereon will damage the insulation of the apparatus.
It is an object of the present invention is to provide a snow melting apparatus which has a satisfactory bending strength and does not impair the joining portion between a road base layer and a road surface layer. Another object of the invention is to provide a snow melting apparatus which is normally operable even if disconnection occurs at one location, and heating wires for melting snow which are excellent in bending resistance property. Yet another object of the invention is to provide a snow melting apparatus which allows the work in a construction site to smoothly be done, and is free from dielectric breakdown. Still another object of the invention is to provide a snow melting apparatus which has good bending resistance property.
To achieve the above objects, there is provided a first aspect of a snow melting apparatus comprising: at least two heating wires bent like U; fixing members for fixing and holding both end portions of the heating wires; and connecting cords for electrically connecting the ends of the heating wires within the fixing members.
In the first aspect of the snow melting apparatus thus constructed, at least two heating wires bent like U are fixed and held with fixing members. The heating wires are fixed at the end portions and keeps a fixed arrangement of them, and may be laid along a curve driveway and the like. Further, no damage is caused to the joining force between a base layer and a surface layer of a driveway, and there is no chance of decreasing a strength of the surface layer.
A second aspect of the snow melting apparatus of the invention comprises: a plurality of heating wires arranged in parallel at predetermined intervals; fixing members for fixing and holding the end portions of the heating wires; and auxiliary fixing members, shaped like bars, for holding intermediate positions of the plurality of heating wires at predetermined intervals.
In the thus constructed second aspect of the snow melting apparatus, a plurality of heating wires are arranged in parallel at predetermined intervals, the end portions of the heating wires are held and fixed with the fixing members, and intermediate positions of the plurality of heating wires are held with auxiliary fixing members, shaped like bars. With this construction, the heating wires keep an arrangement of them while not meandered. Further, there is no chance of impairing the joining portion between a road base layer and a road surface layer, and reducing a strength of the road surface layer. Further, the heating wires are fixed at points with the auxiliary fixing member. Good bending property is secured and it is easy to lay those wires along a curved driveway and the like.
Additionally, in the first and second aspects of the snow melting apparatuses, since a plurality of heating wires are used, if those heating wires are connected by use of connecting cords to form a parallel electric circuit, increase of electric resistance of the whole snow melting apparatus is suppressed. Therefore, there is no need of increasing the heating wires in diameter. Further, if one heating wire is disconnected, there is no chance that the whole apparatus is put to an inoperable state.
Further, if the end portions of the heating wires are electrically connected to connecting cords and power supply cords within the fixing members by means of press-contact terminals, the troublesome work of wiring the snow melting apparatus in the site is eliminated. If the fixing members are made of a rubber material or a resin material, insulation and load-resistance performances of the snow melting apparatus are improved.
When the fixing members are formed by using a rubber material or a resin material, if the end portions of the heating wires connected to connecting cords and a power supply cord, and then those end portions, together with those connecting portions, are covered with a rubber material or a resin material, the fixing members are formed in an integral form. If the fixing members are so constructed, the electric connection portions are buried within the rubber or resin, so that good insulation performance is ensured.
According to another aspect of the invention, there is provided heating wires in which a heating member, which includes a core wire formed with heat-resistance fibers and a heating resistance wire wound around the outer circumference of the core wire in a spiral fashion, is covered with a protecting layer, and the resultant is buried in the asphalt layer of the road. In the heating wires, the end portions of the heating wires are electrically connected to connecting cords and power supply cords within the fixing members by means of press-contact terminals.
In the heating wires, the heating resistance wire are wound around the outer circumference of the core wire in a spiral fashion. Therefore, their bending resistance is excellent. As a result, there is no chance that their resistance value abnormally changes and the wire is disconnected. Further, the end portions of the heating wires are electrically connected to connecting cords and power supply cords within the fixing members by means of press-contact terminals. Therefore, there is no need of troublesome wire connecting work in the site. Accordingly, the heating wires are suitable for those of the snow melting apparatus.
In the heating wires, it is preferable that the core wire is formed with an aromatic polyamide fiber and the heating resistance wire is formed with stainless steel fibers. The combination of those materials presents good bending resistance property.